1. Field of the Invention
The present invention relates to a server and storage system technique and particularly to a storage system having a plurality of storage blades as constituent members and needing high response characteristic, large number of transactions and high reliability.
2. Description of the Related Art
The capacity of a hard disk (HDD) has increased year by year. When HDDs are combined to form a disk system, damage due to failure in one HDD becomes very large. Therefore, a system for achieving high availability with low cost while protecting respective user data from single HDD failure or the like has been demanded. xe2x80x9cPerformance Assessment Study of an Online Reconfiguration of an Autonomous-Disk Clusterxe2x80x9d, The Institute of Electronics, Information and Communication Engineers (IEICE), Technical Report of IEICE, Vol. 101, No. 339 and U.S. Pat. No. 5,463,758 disclose a data storage system of greater capacity.
A chief object of the present invention is to provide a technique for reducing the number of times for retrieving primary and secondary data to suppress lowering of performance in the case where data mirroring is performed in a disk system constituted by a plurality of storage blades.
Another object of the present invention is to provide a technique for improving reliability of a disk system by terminating data write in an early stage of processing in the case where double write of data is performed in the disk system constituted by a plurality of storage blades.
To achieve the foregoing objects, the present invention provides a multiple access storage system having: a plurality of storage blades; and interconnection means for connecting the plurality of storage blades to one another and connecting each of the storage blades to a host system; wherein: each of the storage blades includes a HDD for storing user data or redundant data of the user data, a controller for controlling the HDD, and an I/O port for input/output of a data frame from/to the interconnection means; the controller judges, upon reception of a data access request designated by a data frame given from the I/O port, whether data corresponding to the data access request is stored in the HDD or not, and transfers the data frame to another storage blade having a high possibility of presence of the data corresponding to the data access request when the data is absent in the storage blade; a transmission times region for counting the number of transmission times by which the data frame is transferred between storage blades is provided in the data frame so that a threshold of the number of transmission times is set in each of the storage blades; and if the number of transmission times stored in the transmission times region is not smaller than the threshold of the number of transmission times when a decision is made that the access-requested data is not stored in the HDD, the controller broadcasts the data frame to all storage blades having possibility of presence of the data.